1. Department of Orthopaedic Surgery and Rehabilitation, 985360 Nebraska Medical Center, Omaha, Nebraska 68198-5360, Nebraska Centre for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588, Department of Chemistry, University of Nebraska−Lincoln, 514A Hamilton Hall, Lincoln, Nebraska 68588, and Department of Physics, University of Nebraska, 6001 Dodge Street, Omaha, Nebraska 68182